The Open System Interconnection (OSI) model defines a networking framework for implementing protocols in seven hierarchy layers. Control is submitted from one layer and delivered to the next layer through Service Access Points (SAPs), starting at the Application layer in one station and proceeding to the bottom layer or Physical layer. The seven layers are: an Application layer, a Presentation layer, a Session layer, a Transport layer, a Network layer, a Data Link layer, and a Physical layer. A Media Access Control (MAC) layer is a sub-layer of the Data Link layer and provides information to and/or receives information from the Physical layer, such as demodulated and decoded packets from downlink receiver circuitry. For example, in burst-mode wireless communications, at the uplink side, MAC Service Data Units (MSDUs) are submitted to the MAC layer and the MAC layer creates MAC protocol data units (MPDUs) including one or more fragments of MSDUs. The MAC layer submits the MPDUs to the Physical layer and the Physical layer creates downlink bursts from the submitted MPDUs, the bursts being included in downlink frames. The downlink frames are encoded and modulated for transmission from a transmitter.
The IEEE 802.16 standard provides an Air Interface specification for fixed broadband wireless communication systems which passes packets through a MAC layer, each fragment within the packet being provided a fragmentation subheader for numbering thereof. At downlink reception, fragments are received within a PDU at a Physical layer and passed to the MAC layer as received. The MAC layer is constrained to pass the MSDU to the next layer as ordered fragments.
Packet-based wireless communication systems, however, may communicate packets in bursts and wireless communication systems such as orthogonal frequency division multiple access (OFDMA) systems are particularly susceptible to having packets within multiple downlink bursts possibly interleaved within each other. As MSDUs are being reassembled at the MAC layer, the MAC layer will verify that each fragment of the MSDU being received is received in order. When an out of order fragment is detected, the fragments of the MSDU being reassembled will be discarded. The discarded fragments will either be lost information, decreasing the reliability of communications, or will need to be retransmitted, thereby increasing the time necessary for receiving reliable communications.
Thus, what is needed is a method and apparatus for reordering fragments within a MSDU. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.